Manufacturing menthol



- heating thymol Patented May 17, 1921 UNITED STATES-PATENT OFFICE.

KARL SCHfiLLKOPF OF DUSSELDORF-OBEBKASSEL, GERMANY, ASSIGNOB '10 m1 NISCBE "KAMPFEB-FABRIK GESELLSCHAFT MIT BESCH BAHKTEB HAFTUHG. OI

'DUSSELDORF-OBERKASSEL, GERMANY.

MANUFACTURING HENTHOL.

No Drawing. original application filed November 11, 1.922. Divided and this application In my copendingapplication for Letters Patent Serial No, 603,853 filed November 28th, 1922 and the application divided from it. Serial No. 118,834, filed June 26th, 1.926, I have described the-process for manufacturing racemic menthol. consisting in firstly in presence of catalysts promoting the hydrogenation with hydrogen under pressure, secondlyseparating by physical processes from the reaction product the crystallizable, crystalline racemate of v menthol and thirdly subjecting the remaining liquid, noncrystallizable mixture of isomeric menthols to a new hydrogenation process with catalysts under pressure, if de-' sired after having been added to fresh thymol.

The present process consists in heating thymol in presence of catalysts promoting the hydrogenation with hydrogen under pressure, separating by physical processes from the reaction product the crystallizable crystalline racemate of menthol and heating the remaining liquid, noncrystallizable mixture of isomeric menthols, with an alkaline -metal mentholate to temperatules above 100 degrees centigrade, preferably to 200300 degrees centigrade. The reaction product is distilled 'With steam and the distillate subjectedto a fractional distillation.

I may use as'alkaline'metal mentholate,

potassium mentholate or sodium mentholate 1 and may prepare them from potassium metal or sodium metal, added to any menvthol (for instance the liquid menthol mixture obtained and separated, or' not separated, from the i hydrogenation of thymol) Example: kilo ams thymol are heated with 500-gram's nic el catalysts-( latinum, palladium, cobalt catalysts) with ydrogen to about 200. degrees centigrade .under a pressure of 5-30 atmospheres. I may-carry out the process in an autoclave and agitate the mass. After suflicient amounts of hydrogen having been absorbed, one separates as, 1622, Serial 110. scuba, and in Germany ma filed June 26, 1926. Berl'al No. 118,888.

the product of hydrogenation from the catalysts by distillation or filtration andseparates the menthol from the liquid menthols mixture either by a freezing process or by fractional distillation.

By the freezing process '(for instance at zero or minus-five degrees Centigrade): the

mixture is heated with 300 grams sodium metal during about 20. hours to about 300 degrees centigrade. consistin of about parts by weight inacthe men hol (racemate) and 50 parts by weight liquid menthols mixture is distilled with steam and the distillate is subjected to fractional distillation. One may obtain about 50 parts by weight of'inactive menthol of melting point 34 degrees centigrade.

The liquid menthols mixture separatedfrom the inactive menthol may be added to fresh thymol and subjected to hydrogenation by heating with catalysts promoting the hydrogenation and hydrogen under pressure.

' I claim?- The process menthol which! consists in heating thymol with catalysts promoting the hydrogenation and hydrogen under pressure, separating the inactive menthol from the liquid men- The reaction product,

for manufacturing inactive thols mixture, heating the latter with an alkaline metal mentholate, subjecting" the reaction product to steam distillation. andfractionating the distillate.

v In testimony whereof, Ihave signed my name to this specification.

soHoLLKorF." I 

